Tait TB7100, Руководство по обслуживанию

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TB7100 Service Manual Frequency Synthesizer Fault Finding 147
© Tait Electronics Limited October 2005
11.2 Power Supplies
Introduction
First check that a power supply is not the cause of the fault. There are four
power supplies for the frequency synthesizer — two are supplied from the
PSU (power supply unit) module and two are produced in the synthesizer
circuitry itself:
■
Task 3 : 14 V DC supply from SMPS (
VCL SUPPLY
)
■
Task 4 : 6 V DC supply from 6 V regulator in PSU module (
+6
V
0
)
■
Task 5 : 5 V DC supply following filtering of 6 V supply ( +5
V DEC
)
■
Task 6 : 3 V DC supply from 3 V regulator in PSU module (
+3
V
0
AN
)
The measurement points for diagnosing faults in the power supplies are
summarized in
Figure 11.1 .
Figure 11.1 Measurement points for the frequency synthesizer power supply circuitry
PIN 4 OF
Q508
PIN 4 OF
Q508
PIN 4 OF
IC606
PIN 4 OF
IC606
PIN 5 OF
IC606
PIN 5 OF
IC606
Q500 AND
R533
Q500 AND
R533
PINS 7 AND 15
OF IC503
PINS 7 AND 15
OF IC503
SIGNAL TYPES
RF
ANALOG
CLOCK
DIGITAL
PLL
14 V
SMPS
LOOP
FILTER
AND
SUMMER
FILTERING
OF SUPPLY
FOR PLL
AND LOOP
FILTER
FILTERING
OF SUPPLY
FOR VCO
CIRCUITRY
3 V
SUPPLY
VCO
CIRCUITRY
FREQUENCY
SYNTHESIZER
INTERFACE
CIRCUITRY
INVERTER
JUNCTION OF
C531 AND R530
JUNCTION OF
C531 AND R530
+3V0 AN
L506
9 V
SUPPLY
6 V
SUPPLY
AGND
+9V0
+6V0
VCL SUPPLY +5V DEC